China has tightened its censorship of online news services and bulletin boards, a move analysts say reflects its fear of a burgeoning civil society.

The government already monitors the net for sensitive issues such as Taiwan and democracy, but the new rules also forbid content harming "social order".

This includes posts which advertise unregistered protests and groups.

China has about 100 million internet users, some of whom are proving adept at avoiding government control.

Nascent civil society (is) the explicit target in terms of repression

Nicolas Becquelin, Human Rights in China

News service providers, including those which offer bulletin boards or send news stories to mobile phones, will be subject to the new regulations, the China Daily reported.

Nicolas Becquelin, research director at Hong Kong-based organisation Human Rights in China, said the rules "certainly don't go on the right direction, but they're not surprising".

They "make nascent civil society the explicit target in terms of repression," he said.

He added that the government's power to block content through technology was limited, but that it had a powerful weapon in the public's use of self-censorship and the fear it generated by example.

A journalist was recently jailed for 10 years for sending foreign-based websites the text of an internal Party memo. The journalist, Shi Tao, is believed to have been jailed as a result of information Western internet firm Yahoo supplied to the Chinese government.